Janet Kwasniak's blog on consciousness and the brain

Doing a task while asleep

A recent paper (citation below) describes subjects working away at a task, categorizing words, while asleep. Here is the abstract:

Falling asleep leads to a loss of sensory awareness and to the inability to interact with the environment. While this was traditionally thought as a consequence of the brain shutting down to external inputs, it is now acknowledged that incoming stimuli can still be processed, at least to some extent, during sleep. For instance, sleeping participants can create novel sensory associations between tones and odors or reactivate existing semantic associations, as evidenced by event-related potentials. Yet, the extent to which the brain continues to process external stimuli remains largely unknown. In particular, it remains unclear whether sensory information can be processed in a flexible and task-dependent manner by the sleeping brain, all the way up to the preparation of relevant actions. Here, using semantic categorization and lexical decision tasks, we studied task-relevant responses triggered by spoken stimuli in the sleeping brain. Awake participants classified words as either animals or objects (experiment 1) or as either words or pseudowords (experiment 2) by pressing a button with their right or left hand, while transitioning toward sleep. The lateralized readiness potential (LRP), an electrophysiological index of response preparation, revealed that task-specific preparatory responses are preserved during sleep. These findings demonstrate that despite the absence of awareness and behavioral responsiveness, sleepers can still extract task- relevant information from external stimuli and covertly prepare for appropriate motor responses.

This study does not address whether a task can be initiated while asleep because the subjects fell asleep while engaged in the task. And, of course, as movement is blocked during REM sleep, the initiation of movement while unconscious was also not tested. What was tested was the processing required to carry on the task and prepare for movement.

Some previous postings have looked at unconscious processes. Some experiments used unconscious priming to test whether such priming can result in particular processes. In (does control of cognition have to be conscious?) it was indicated that control of cognition (conflict adaption) can be unconscious and in (unconscious effects) it was shown that unconscious priming could be responsible for perceiving, doing semantic operations and making decisions. Other experiments have used control over the use of consciousness by forcing its content. In (discovering rules unconsciously) blocking the use of consciousness for a particular problem showed that unconscious processing was superior to conscious processing for discovering ‘grammatical’ rules. Now we have a third method, the comparison between awake and asleep states showing that task-related processing can proceed unconsciously, starting from perception, through processing and decision making to preparation of motor responses.

It is not news any more that most of the processes in the brain can be done unconsciously. We are not aware of these processes, naturally, because they are unconscious, but that does not mean they do not happen. The bulk of the brain’s activity is unconscious. We should not be surprised at unconscious thought. The exceptions that, to date, appear to require consciousness are the formation of explicit memories, the use of working memory, and the particular form of awareness that we associate with consciousness. Perhaps consciousness has more to due with a particular use of memory rather than a particular type of thought process.